Walker’s leadoff homer in the second was the only hit off Buchholz, who struck out four and walked two in five innings.

Sanchez homered in the seventh against Chris Carpenter, and Michael McKenry hit a solo drive off Oscar Villarreal in the eighth.

Pirates starter James McDonald labored in the first, when Ryan Lavarnway hit a two-run single, then retired 11 of 14 batters. He gave up four hits and three walks in five innings and struck out six.

After recovering from a stress fracture in his back in 2011, Buchholz began last season by going 4-2 with a 7.19 ERA in his first 10 starts. He was 7-6 with a 3.45 ERA the rest of the way.

After watching video of Buchholz’s early outings, Farrell said he saw a lot of pitches up in the zone.

“Maybe he was subconsciously protecting (his back) or just couldn’t get full extension to drive the ball downhill,” Red Sox manager John Farrell said. “But after his seventh or eighth start, he ran off good numbers, like he was his old self. That’s what we’re seeing now.

“He’s gone through a pretty drastic transformation from the way he pitched in the minors and in his rookie year to now,” Farrell added. “The last couple outings, when he puts the ball on the ground, he’s at his best. That’s when he’s most relaxed.”

Meanwhile, McDonald had a rough start but wasn’t rattled. “I got locked back in, kept my composure and finished strong,” McDonald said. “I didn’t let the game get away from me. I felt confident – every pitch, every moment out there.”

This was the second game in a row that McDonald overcame a rocky first inning.

“It’s definitely correctable,” Pirates manager Clint Hurdle said. “He’s got some weapons. With James, it’s about rhythm, pace and timing. We’ve got to keep him working and take the cerebral part out of it.”

McDonald has a 4.19 ERA in five games with 4 strikeouts in 19 1/3 innings.

NOTES: The start of the game was delayed by 48 minutes, but it didn’t start raining until after the tarp was removed and play got under way ... Red Sox left-hander Franklin Morales (bulging disk) threw from 60 feet.” If we can repeat that a couple of days, we’ll have more insight on what plan to follow,” Farrell said.